.background{
    background-image: url(../img/maoxuewang_backgournd.jpg);
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    height: 250px;
    width: 100%;
}
.text_main,.main_li{
    width: 1050px;
    text-align: justify;
    font-size: 16px;
    margin: 20px auto;
}
.main_li>h2{
    color: red;
    font-size: 20px;
    font-weight: 600;
    box-sizing: border-box;
    height: 30px;
    border-bottom: 1px solid lightgrey;
    margin: 20px 0;
}
.main_li_1{
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    text-align: center;
}
.main_li_1>ul{
    margin: 0 0 20px 0;
}
.main_li_1>ul>li:nth-of-type(1){
    width: 240px;
    height: 230px;
    overflow: hidden;
}
.main_li_1>ul>li{
    height: 20px;
    line-height: 20px;
    margin: 5px 0;
}
.main_li_1>ul>li>a>img{
    width: 240px;
    height: 230px;
    transition: 0.5s;
}
.main_li_1>ul>li>h3{
    color: #000;
    font-size: 16px;
    font-weight: 500;
}
.main_li_1>ul>li>a{
    color: #707070;
    font-size: 14px;
    text-decoration: none;
}
.main_li_1>ul:hover img{
    transform: scale(1.1);
}
.main_li_1>ul:hover a{
    color: red;
}
.main_li_2{
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
}
.main_li_2>a{
    display: block;
    height: 40px;
    width: 150px;
    line-height: 40px;
    font-size: 16px;
    box-sizing: border-box;
    border: 1px solid #000;
    color: #000;
    text-align: center;
    text-decoration: none;
    margin: 10px;
    border-radius: 5px;
}
.main_li_2>a:hover{
    color: red;
    border: 1px solid red;
}